The present invention relates to an electronic compressed-air system for vehicles.
WO 98/47751 A1 describes a pneumatic vehicle brake system provided with a compressor, at least one air-load circuit, such as service-brake circuits, a parking-brake circuit, a low-pressure auxiliary circuit and a high-pressure circuit, wherein the circuits are provided with compressed-air reservoirs and demand valves. Between the compressor and the at least one load circuit, there are disposed first electrically actuatable valves, which are closed in the de-energized normal state, and, between the compressor and the auxiliary circuit, there is disposed a second electrically actuatable valve, which is open in the de-energized normal state. The valves are actuated by an electronic control unit. The outlet ports of the first valves of the air-load circuits are in communication via check valves with the outlet port of the second valve, which is open in the de-energized normal state. If a compressed-air demand exists in one of the load circuits, for example due to too-low reservoir pressure, the corresponding valve is activated by the control unit, whereby the air demand is covered by the compressor, while at the same time the second valve of the auxiliary circuit is closed. Failure of the compressor leads to a pressure drop, which is detected by the control unit, which closes the valves or keeps them closed, whereby the pressure in the circuits is maintained. A pressure-regulating valve determines the pressure level. In the event of failure of the pressure-regulating valve, overpressure is relieved via an overpressure valve. Pressure sensors monitor the circuits. The circuits are supplied with air via the second, normally open valve and via the check valves connected upstream from the circuits. If the electrical system fails, all valves go to normal state. Nevertheless, the compressor continues to run and supplies the circuits with air via the second, normally open valve of the auxiliary circuit, the system pressure being determined by a low-pressure relief valve of the auxiliary circuit. If one valve fails, the associated circuit can be supplied with air via the valve of the auxiliary circuit and the check valve. The known system is complex, since each load circuit is equipped with its own compressed-air reservoir.